Optical sensor arrangements are used for measuring at least one observable, where the observable can be the presence of a specific substance or other physical properties, such as changes in pressure or temperature. Some optical sensor arrangements include optical resonance circuits, which include at least one optical resonator, such as an optical microring resonator, as a very sensitive optical sensor type for sensing the observable. In many cases the resonator is exposed to a medium such as a gas or a liquid, where the medium may carry a chemical compound, a biological substance, or the like, to be measured by the optical sensor arrangement. In several cases the optical resonator is covered by a covering material (or active layer) which includes an active material such that molecules of the substance to be detected can dock at the active material.
Optical resonators have the property of allowing light of a specific frequency that represents a resonance frequency of the optical resonator (i.e., the wavelength of the light multiplied by an integer corresponds to the effective refractive index multiplied by the length of the resonator) to enter the optical resonator while light of other wavelengths does not enter the resonator.
Many optical resonators have the property that when a physical condition, such as temperature or pressure, of the surrounding medium changes or a substance, such as a chemical or biological compound or substance, attaches to at least one of the surfaces of the resonator, the optical length of the optical resonator changes with it, i.e., the resonance frequency of the optical resonator is shifted. The shift in resonance frequency or optical length can be used to determine whether the observable to be sensed has changed or is found in the medium.
A problem to be solved is to design an optical sensor arrangement for measuring an observable and provide an alternative solution to the optical sensor arrangements found in the prior art.